Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
Grey box = effect estimates from single studies. Diamond = pooled result with confidence interval. Vertical line at ‘1’ on the x-axis is the line of no effect. Weight (in %) = influence an individual study had on the pooled result.
